Stomatal pores in the epidermis of plant leaves enable the control of plant water loss and the influx of CO2 into plants from the atmosphere. Carbon dioxide is taken up for photosynthetic carbon fixation and water is lost through the process of transpiration through the stomatal pores. Each stomate is made up of a specialized pair of cells named guard cells, which can modify the size of the stomatal pore by controlling guard cell turgor status.
An important trait in agriculture, in biotechnological applications and the production of biofuels is the water use efficiency of plants. The water use efficiency defines how well a plant can balance the loss of water through stomata with the net CO2 uptake into leaves for photosynthesis and hence its biomass accumulation. Several biotic and abiotic factors influence the state of stomatal opening as well as stomatal cell density, thereby optimizing the water use efficiency of a plant in a given condition. The concentration of CO2 regulates stomatal density, where high levels of CO2 will lead to a decrease in stomatal density.
WO 2008/134571, Schroeder et al., describes compositions and methods for manipulating the exchange of water and/or carbon dioxide trough plant stomata by controlling carbon dioxide sensor genes. The document provides compositions and methods for opening or closing a stomatal pore on a guard cell in the epidermis of a plant.